MAC header
Machine language
Magnetic card reader
Magnetic ink character recognition [MICR]
Magnitude
Mail relay server
Mainframe
Malware
Management
Management information system [MIS]

Mandatory access control [MAC]
Man-in-the-middle attack
Manual journal entry
Mapping
Masking
Masqueraders
Master file
Material misstatement
Material weakness
Materiality

Maturity
Maturity model
Maximum tolerable outages [MTO]
Measure
Media access control [MAC]
Media access control (MAC) address
Media oxidation
Memory dump
Message authentication code
Message digest

Message digest algorithm
Message switching
Metric
Metropolitan area network [MAN]
Microwave transmission
Middleware
Milestone
Miniature fragment attack
Mirrored site

Mission-critical application
Misuse detection
Mobile computing
Mobile device
Mobile site
Model
MODEM (modulator/demodulator)
Modulation
Monetary unit sampling
Monitoring policy